Process of treating tin sulphide concentrates



Dec. 12,1944. E LEBEQEFF Y f 2,364,727

PROCESS 0F TREATING TIN SULPHIDE CONCENTRATES Filed Feb. 29 1944 Y INVENTOR.

Patented Dec. 12, 1944 UNITED STATE PROCESS OF TREATING TIN SU'LPHIDE CONCENTRATES Yurii E. Lebedefl, Metuchen, N. I., assignor to American Smelting and Refining Company, New York, N. Y., a corporation of New Jersey Application February 29, 1944, Serial No. 524,394

(Cl. 'i5-85) 11 Claims.'

This invention relates tol a process for recovering metallic tin from tin ore concentrates or metallurgical by-products containing tin and more particularly to a process for treating sulphide-tin complexes lto recover the tin as tin metal or suitable alloy.

In the methods normally employed for smelting oxide tin ore vconcentrates to recover the tin the general practice is to smelt the tin ore concentrates with silica, lime and carbonaceous reduction fuel to yield tin metal and slag. When such ores contain even small amounts of impurities, impure tin metal and 'slags relatively high in tin are produced. Additional processing of the tin metal and tin-containing slag is necessary to obtain a` suitablegrade of tin metal and a slag sufficiently low in tinto permit it to be discarded.

When oxide tin materials contain deleterious .amounts of iron and other impurities, it is customary to give them some preliminary treatment, as by leaching with acids, to remove the impurities. With large amounts i. of impurities the cost of this becomes prohibitive.

None of the above methods is applicable to sulphide ores unless they are rst roasted. For low grade oxide or sulphide complex tin ore concentrates or metallurgical by-products .containing large amounts of iron and otherv impurities no satisfactory method of treatment is known. Various methods have been tried but ythey are all complex and very costlyto operate.

It is an object of the present invention to provide a relatively inexpensive and simplified method of treating tin-bearing concentrates containing sulphur and iron and/or tin sulphide matte `containing impurities including iron to the tin contained in a fused sulphide matte is recovered as tin metal. or alloy which is substantially .free from iron and sulphur, by the addition of controlled amounts of metallic iron or othersuitable substances containing iron in metallic form.

The reaction which takes place with the inn troduction of metallic iron according to my process is thought to be a chemical replacement effect, that is, the tin in the tin compounds of the sulphide matte is replaced byv iron, lthe tin being released or precipitated as vmetallic tin which collects in a. separate layer beneath the molten matte. This displacement reaction, like -most chemical reactions of this kind, is a recontained in the precipitated tin metal may be recover the tin as tin metal or an alloy low in be particularly pointed out in the' claims appended hereto, the invention itself, as toits further objects and advantages, and the manner in which it may be carried out, may'be better understood by referring to the following description and accompanying drawing forming a part vthereof in Whicha ow sheet of the process of thsinvention is shown for purposes of explanation.

According to my invention practically all of illustrated by the chemical equation:

Tin sulphide-i-metallic iron'i:2

' iron sulphide-i-tinimetal) In the vequation the unreacted metallic iron becomes alloyed with the metal phase providedv controlled so that the metal phase is 'kept low in iron, the corresponding sulphide slag rphase is then found to be high in tin. The latter result may be overcome by resorting to a multistep counter-current process wherein the hightin sulphide phase is returned.forretreatment.` In this manner the desired end products ymay beV produced but at the expense of additional operations.

Where degradation of the precipitated metal phase is' permissible, however, the equilibrium reaction can be made to proceed further to the right by decreasing the concentration of tin in the metal phase.v This may be accomplished by simply introducing other metal or metals which will alloy with the precipitated tin metal, the

added metal actingas a. diluent. .Furthen ifthe tin forms an intermetallic compound or a series of compounds with the degradant metal, or metals the reaction equilibrium shift to the right l may be accentuated. `By introducing iron precip# itable metals other than tin the concentration of the tin in the alloy metal phase of the smelted charge is decreased permitting the production of 'an iron sulphide matte low in tin and a tin alloy metal low in iron in one operation.

In accordance with one embodiment of my invention I take advantage of the -effect produced by the presence of diluent metals in processing tin sulphide complex'c'oncentrates where-- by the'tin is recovered therefrom as tin metal oralloy which is low iu'ironand sulphur by a onestep treatment ofthe fused matte with metallic'iron. Where,` however, the ore or metal" lurgical .product being treated contains tin, sulphurV and iron but none or only minor amounts of metals,'other than tin which are precipitable bymetallic iron, arid sumcient metallic iron is cipitable by metallic iron, such as bismuth,'

arsenic, antimony, lead, copper, silver, gold, etc., preferably controlled amounts of one o1 more of these iron replaceable substances is introduced into the charge to act as a diluent or degradant of the tin-so that by a single treatment of the fused tin sulphide matte with metallic iron there may be producedaniron sulphide matte con- .fused liquid matte.

terial in sufcient amount to replace the tin,k

As typical examples illustrating how my process may be practiced the following `is given:

Example 1 One hundred thousand poundsk of tin sulphide complex concentrate analyzing 11.2% Sn, 15.0%

Cu. 6.2% Sb, 1.0% Pb., 0.8% Bi, 0.5% As, 14.7% Fe, 34.8% S, 1.7% SiOz, 0.9% CaO and 1010.0

oz./T Ag with traces of Au was smelted in a reverberatory furnace'at a temperature of about l800.to 2000" F. with 20,000 lbs. of sodium carbonate and 2,000 lbs. of coke so as to form 'a To this molten charge was introduced 45,000 lbs. of metallic iron in the form of clean wire analyzing 55% metallic iron and 45% copper. During smelting and-the reaction of the molten charge with the irorrwire the dust collected from the `fumes given off amounted to 10,250 lbs. which assayed about 20% Sn with other Values and impurities. Tin metal alloy tapped from the furnace after-.the iron had reactedwith, the charge weighed 20,250 lbs. and analyzed 25.6%l Sn,`39.5% Cu, 18.8%. Sb, 2.2% Pb, 0.9%,S, 0.7% As, 1.0% Fe, 2.1% Bi, and

A2510.0 oz./T Ag.

The slag matte by-product produced amounted to 114,000 lbs. analyzing 0.95% Sn,34.3% Fe, 20.6% S, the remainder being made` up of Cu,

Pb, As, Bi with a small amount of silver. This slag matteA is processed by standard converting methods for recovery'of metal values such as copper and silver where they are present in suf- 'taining less than 1% tin and a tin metal alloy phase comprising-less thanl 1% iron and 1% or less of sulphur. l It hasbeen further found that the equilibrium can be moreA readily displaced in the desired direction in the presence of certain' iiuXes and conditionerssuoh as alkaline or alkaline earth compounds which'will react with the charge to form alkaline or alkaline earth sulphides. For example, lime or sodium carbonate may be used, the latter being preferable because `of its greater fusibility. i

While it has not been uncommon to add metal powders, suchl as metallic iron, zinc, and/or carbon or thelike to oxide slag-tin metal systems, such as in the reduction'of cassiterite, to reduce the'tin oxide present, 'the advantageous results produced by my invention are not obtained. By employing the process 'of thisinvention, however, tin ore concentrates and other vtin-iron bearing materials can be processed in an ordinary reverberatory furnace heated in the f fconventionalmanner. Further, in practicing the '.reduction of tin joxideslag systems using metal powdersr and carbon additionsit `is practically im y possible' to produce a =discard "slag containing `lessxthan.1% tin. :This is`,however,' readily acl" complished, according to my inventionfby'formr ingV a 'sulphide 'itin Amattefand:smeltingy it with metallic iron or any suitable iron bearing maflcient amounts, otherwise the slag `matte is discarded. The tin-copper-antimony alloy which y.contains only 1% iron and less than 1% sulphur is processed to recoverthe tin, where desired, by

, employing conventional methods.

i Example' II the total metallic iron required was added to the fused sulphide charge and, after it had reacted, cleantin alloy metal which was relatively free from Fe and S was tapped from under the liquid tin bearing soda matte. metallic iron in excess of that required to replace the tin remaining in the matte was introduced` .by this excess iron addition which vwas left in ironaddition method is employed when there are insufficient amounts of diluent metals precipitable by metallic iron present in the tin-iron sul- 'fphide'complex toeifectively limit .the tin content of the matte produced. 4

Thereafter ladditional phur should be present to react with all the iron to form a suitable matte of proper iluidity.`

The quantity of uxing substances such as soda, lime or the like, required to be ladded may vary for producingv the best results.. Usually soda ash amounting to from l-to 30% by Weight of, the tin concentrate is used, howeveigwherelthe concentrate contains relatively large amounts of ux forming substances little or no soda or the like uxing agents may be necessary. I have found it4 expedient when treating complex ore concentrates according to my invention, and which containaround three percent orlless of fluxing-material assaying SiOz and vCaO, to addi-approxif mately 20% by weight of sodiumcarbonate and vabout 2% coke.- Carbonaceous-fmaterial in small amount is usually employed tocounteract the -oxidizing atmosphere of the furnace, however, if

the furnace is operated under reducing conditions the addition of carbon may be omitted.

The amount of metallic iron required will vary depending upon the Vcontent, of iron precipitable 'v .taining 1% or'less of tinand a tin*v metal phase en A containing less than Y1%y Iiron and'less than 1% sulphur, and separatingsaid soda-iron sulphide matte lphase from the N tin metal phase to recover said tin metal.

2. A pyrometallurgical process for treating tin bearing materials containing sulphur andiron in substantial` amounts to, recover tin metal,V comprising intermixing with the tin-bearing material .awquantity of sodium, carbo'n`ate up to 30%, a

. `quantity of coke up to 21/2% said soda and `coke 1% of iron added being based upon the. Weight of the tinv bearing material used, smelting the mixture in a.

reverberatory furnace to produce a tin sulphide soda-iron matteand thereafter reacting the mol- `ten matte with metallic iron to replace Ithe tin and ironprecipitable metalsin they matte and `produce a discard slag matte containing 1% or less of tin and aftin metal containing less than ties.

3.` A. pyrometallurgical rprocessr Whichrcomprises intermixing With'Y tin containing-,sulphide Q mvaterial a quantity of sodium carbonate up to %,'a quantity of coke upto 2.5%, said soda and f tin sulphide `concentrate treated,bvvhereby to form a=smeltable chargesmelting lthe charge lin metals present in the tin sulphide concentrate.

In general, thetotal metallic iron added will amount to from 15 to 30% by weight of the tin ore concentrate being treated. AAs a typical guide I have found in treating a tin ore concentrate comprising approximately 15% Sn, 35% S, 15% Fe and a total of about 25% of iron precipitable metals, i. e. Cu, Sb, Pb, Bi, As, Au and Ag, that the totalmetallic iron added in a one-step process amounted to approximately 25% by weight of the tin sulphide complex of the charge. The amount of metallic iron required may vary depending upon the metals present other than tin. which alloy with tin and are reducible by metallic iron. Enough metallic iron is introduced either as a one or two-step method to produce a final matte containing 1% or less of tin.

From the foregoing it will be observed that I have devised a relatively simple and efficient method for treating tin bearing materials containing iron and sulphur to recover tin metal substantially free from or low in, iron and sulphur. In addition it will be seen that my new process provides a novel procedure for recovering tin metal from tin sulphide matte and producing a final discard matte markedly low in tin Whereby the loss of tin through the matte by-product is for all practical purposes substantially eliminated.

It will be understood that I desire to comprehend within this invention such other changes and modifications as may readily suggest themselves to those skilled in the art and which come within the scope of the appended claims.

What is claimed is:

1. A pyrometallurgical process for treating tin bearing materials containing sulphur and iron as impurities tov recover tin metal which comprises intermixing with the tin-bearing material 10 to 30% of sodium carbonate and smelting the charge to form a tin sulphide-soda-iron matte, introducing metallic iron into the molten mass coke additionbeing based` upon the weightof the a reverberatoryfurnaceat smelting temperatures to` produce` a tin-soda-iron matte, introducing iron metal in the smelted charge insufficient amount to producea tin metal phase containing less than 1% Fe and less than 1%-,sulphur, withdrawing said low iron and sulphur tin metal, add- Y y ing more metallic iron in sufficient amount to produce arsulphidematte .containing 1% or less of tin which matte maybe discarded vand a tin metal phase relatively high in iron-which is left in the furnace and smelted with the succeeding charge. y

4. A pyrometallurgical process for treating tin bearing` material containing relatively large amounts of iron and sulphur and metals precipitable by metallic iron as impurities, comprising intermixing said tin-bearing' material with sodium carbonate in sufiicient amount to produce a uid sulphide matte upon smelting the mixture and adding carbonaceous material to said mixture to reduce any oxides present or formed during the smelting operation, smelting the charge in a reverberatory furnace While collecting any fume produced for recovery of metal values, adding metallic iron to the molten charge in suflcient quantity to replace the tin constituent-of the tin sulphide soda-iron matte so that-it will contain l1% or less of tin, separating the thus formed low tin soda-iron matte whichA contains less than 1% tin andv withdrawing the tin metal alloy `therebeneath which assays less than 1%' Fe and less than 1% sulphur, said tin alloy lcomprising substantially all the other metals present f' which are selectively precipitable by the addition of iron. q l

5. A pyrometallurgical process which comprises intermixing with tin bearing complexes which contain sulphur and iron as impurities and to-v 'insuflocient amount to react with saidmattev Aand produce a soda-iron sulphide matte phaseconand less thanI l%y sulphur as impuri imating 1800 to 2000 F. to produce a tinsulfi phide soda-iron matte, adding metallic iron to the molten charge and reacting it with said matte to cause substantially all thev tin in said tinsull phide soda-iron matte to be replaced with iron whereby a soda-iron sulphide matte is produced which contains 1% or less of tin and substantially all the sulphur and iron of the charge,r a`nd ,l wherein a tin metal alloy product is formed containingl% or less of Fe and 1% or less vof S, the

' tin being alloyed withiron precipitable metals present in said tin bearing complex.

6. A metallurgical process according to claim 5 y wherein at least a portion of the metallic iron 'l5 iron and formed as a by-product of a preceding v added to the molten chargeis tin metal high in smelted charge.

..-"-'7. A metallurgical process according to claim 5 wherein the metallic iron is added in at least two stages `and wherein the lastaddition of metallic iron is in excess of the metallic iron required to replace the -tin' sulphide in thev tin-soda-iron matte whereby a'. sulphide matte is produced containing less than 1% tin which may be discarded and a phase composed of ,tin metal bullion low in Fe and S and a nal tin metal product high in Fe which may be reacted with the vsufciveeding charge.

8. A metallurgical process according to claim` 5 wherein-th`e iron precipitable metals present have been added to the tin bearing material as a diluent to cause a decrease in the concentration of the tin in the alloy metal phase produced during smelting whereby there is formed a matte low 'in tin'and a metal alloy low in iron by one addition or treatment of the smelted charge with metallic iron.

9. A metallurgical processffor treating tin bearing material to recover` tin alloy metal which comprises intermixing with said tin bearing material a quantity of sodium carbonate up to ing the mixture in a reverberatory furnace at a temperature approximating 1800 to 2000 F., adding metallic iron bearing material to the smelted charge and reacting it with said matte to cause substantially all the tin in said tin sulphide sodairon matte tol be replaced with iron whereby a Ysoda-iron sulphide matte is produced which contains 1% or less of tin and substantially all the sulphur and iron of the charge, and wherein a tin metal alloy product is formed containing 1% or less of Fe and 1% or less of S, the tin being n alloyed withiron precipitable metals present in said tin bearing material.

10. A pyrometallurgical process for treating tin containing complexes which contain sulphur and iron as impurities together with alkali uxing substances comprising Vadding a small f which contains 1% or less of tin and substantially all the sulphurl and iron of the charge, and Wherein\an alloy tinfmetal phase is produced containing approximatelyI less-than 1% of iron and y approximately `less than r1% sulphur with the tin forming anl alloy with the tin precipitable n metals present in the charge, and drawing off and sulphur suicient to form a tin sulphidesoda-iron matte upon smelting the mass, smeltsaid tin alloy metal'to recover the relatively pure tin alloy. I y

11. A metallurgical process according to claim '1 'wherein sulphur is addedf to the tin-bearing .Y

material in order to assist in forming the tin sulphide-soda-iron matte which is reactedlwitn the metallic iron to replace substantially all the tin of said matte with iron.

YURII E. LEBEDEFF. 

